A conventional path control technique for a network has following problems: (a) it is impossible to detect routes being congested, in advance; (b) symmetric routing in uplink and downlink cannot be forcibly carried out; (c) it is impossible to reflect the state of a server in routing; (d) it requires a load and/or time to check the states of routes; and (e) it requires a load and/or time to carry out a dynamic processing. Especially, because the Internet, which has come into wide use in recent years, has developed without considering the entire efficiency improvement, it has a lot of problems in efficiency. For example, as for the routing and switching, because autonomous operations are assumed, the protocol is complicated, and there are a lot of case in which the state in the network is not unknown.
In order to solve these problems, the application of MPLS (Multi Protocol Label Switching) has been studied. However, because (a) different routing policies are used for respective domains; (b) an administrator requests not to open the state of a network to other domains; (c) the mutual operation of MPLS may be unstable or the like, MPLS has not been applied to routing between different domains.
Further, US 2002/0051449 discloses a technique for solving the aforementioned problems in the path control for an inter-domain network. More specifically, in the path control for the inter-domain network, by allowing to acquire path information with a network resource in a destination domain in addition to path information with a network resource in an inter-domain and a source domain, it is possible to select a path considering network resources of End-to-End, and to select the optimum path in not only the transmission direction but also the reception direction. Furthermore, by allowing to acquire information on the processing load of a service node in addition to the network resource, it is possible to select the optimum server using such information and the network resource, and to select the optimum path to the optimum destination server. However, this publication does not study MPLS. Moreover, because in this technique, routing is carried out according to a routing protocol, a large amount of load is necessary for routers.
As described above, conventionally, the path control between domains, to which MPLS is applied, has not been studied. Therefore, there are problems in which in communication between domains, to which MPLS is applied, it is impossible to carry out the optimum routing of End-to-End, to avoid network congestion, and to carry out symmetric routing.